Not Applicable
Specular hematite (specularite) is a gray to black, shiny material that is popular, in the form of beads, as bracelets or necklaces. It is desirable to engrave beads to enhance their value. However, hematite poses peculiar problems. It is hard and tends to fracture. For this reason, techniques known heretofore for engraving diamonds, (see for example U.S. Pat. Nos. 6,211,484 and 4,467,172) are not immediately applicable to engraving of specular hematite. At the same time, components of the diamond engraving apparatus described in Pat. No. 6,211,484 and 4,467,172 are common to the apparatus used in the practice of the present invention, with the changes indicated in the following description of the preferred embodiment. It has been proposed to fuse to a substrate by laser a portion of a layer of powdered (iron brown) hematite (see U.S. Pat. No. 6,238, 847), but that is quite a different matter from engraving specular hematite.
In accordance with this invention, generally stated, a method of engraving a specularite bead is provided comprising focusing on the bead a pulsed laser beam with a beam width of 0.005 to 0.006 inches, a wave length of about 1064 nm at an intensity of 60 to 90 watts of power, and a pulse rage on the order of 2000 per second, and moving the beam in a controlled pattern, preferably at about 1.0 to 1.5 inches per second.